In infectious diseases of humans, cattle, poultry, and fish caused by causal bacteria such as Staphylococcus aureus, hemolytic Streptococci, Bacillus anthracis and Clostridium tetani, antibiotics or synthetic antibacterial agents including penicillins, tetracyclines, macrolides, cephalosporins, and cephems have conventionally been used.
Prolonged terms of use or a large amount of use of these conventional antibiotics or synthetic antibacterial agents, however, causes drug resistance to the aforementioned causal bacteria. Especially, methicillin-resistant Staphylococcus aureus (MRSA), which causes a high death rate due to its strong toxicity, has become a big social problem, for it exhibits resistance to multiple drugs and makes therapy difficult.
The object of the present invention is to solve the aforementioned problem and to provide a compound having enhanced antibacterial activities against gram-negative bacteria and gram-positive bacteria, inter alia, gram-positive bacteria--such as Staphylococci--which have acquired drug resistance, as well as antibacterial compositions and drugs containing the compound.
The present inventors conducted extensive research to attain the above object, and found that certain ketonitrile derivatives having the below-described structure exhibit high antibacterial activities against gram-positive bacteria such as Staphylococci and Streptococci, as well as gram-negative bacteria, and that the derivatives are useful as drugs for the therapeutic treatment or prevention of a variety of infectious diseases and as antibacterial agents for diversified materials such as fibers, leading to completion of the invention.